Computer has been widely used by individuals and companies nowadays. When the computer is in use, in order to avoid the keyboard from occupying too much desktop space and take into account of ergonomics to prevent users from hand injury caused by taking the same posture for a long period of time during operation, a keyboard support bracket has been developed to suit user's posture and hand position, and to make adjustment endlessly.
There are plenty of keyboard support brackets proposed in the prior art. For instance, U.S. Pat. No. 4,616,798 discloses an adjustable support for CRT keyboard. It has a bracket holding a keyboard and connecting to a parallelogram linkage located underside a desk. Because the parallelogram linkage is fastened to the lower side of the keyboard support bracket, the space between the bottom and the floor is limited. Leg room is not adequate to accommodate leg movements of users.
U.S. Pat. No. 5,257,767 discloses an adjustable support mechanism for a keyboard platform. While it addresses the shortcomings of the aforesaid patent and uses a non-parallelogram linkage to increase the leg room, its linkage mechanism is still fastened to the lower side of the keyboard support bracket, and the increased space is limited.
U.S. Pat. No. 5,924,664 discloses a keyboard support mechanism which tries to improve the two patents mentioned above. It consists of a mounting bracket, a mounting bracket support in combination with a swivel bracket, a shelf bracket, an upper arm at least one side arm and at least one stopping means. It generates a linkage motion through four pivot points, and the side arm and the stopping means have corresponding connection concave surfaces to generate friction forces to produce locking and positioning effect. However it still has problems remained to be overcome, notably:
It still adopts a conventional parallelogram or non-parallelogram linkage with four pivot points linkages to pivotally connect to one another to achieve endless vertical movement. The side arm is extended to form an arched end to produce a friction force on a first side of the stopping means to achieve positioning. As the side arm and the stopping means are made of metal, in terms of applying forces easily and providing frictional forces required for latching, they cannot generate a desirable coordination during the movement. The metal also generates heat and noise under friction. The arched end tends to wear off after used for a long period of time.
In addition, according to ergonomics, when the keyboard is under operation, the forearm of users must be in parallel with the back of hands. To make the support bracket to support hands nicely, the support bracket also is preferably in parallel with the forearm. However, all the support brackets in the prior art has the side arm forming a constant angle relative to the floor (generally tilting upwards about 3 degrees, referring to U.S. Pat. No. 5,924,664, item 54). Based on user's perspective, the forearm inclines downwards gradually from the position adjacent to the desktop to the operation position. If the support bracket does not alter the angle, the support effect of the support bracket to the wrist and forearm diminishes gradually. As a result, it could cause injury to users when operating in such a posture for a long period of time.